1. Field of the Invention
The present invention relates to an amorphous polyamide resin composition that is excellent in transparency, heat resistance, and stiffness and a molded product thereof.
2. Description of the Related Art
Conventionally, transparent resins are used as materials for molded products required to have usual transparency, such as automotive parts, lightning equipment, and electrical parts. In recent years, particularly, the range of applications of the resins as optical materials required to have excellent optical properties has been extended. In particular, an amorphous polyamide resin derived from a structure with polymerized monomers has low birefringence and high transparency, and hence the resin is used as a transparent resin for optical materials, and the like.
However, the amorphous polyamide resin has low stiffness. Therefore, attempts to improve the stiffness of the amorphous polyamide resin molded product have been made by addition of a fiber reinforcing material such as a glass fiber, an inorganic filler, a rubber component, or the like.
For example, Japanese Patent Application Laid-open No. Hei 4-337355 discloses an amorphous polyamide resin composition produced by blending a glass filler such as a glass fiber in an amorphous polyamide resin composition containing a transparent polyamide resin and a styrene-butadiene copolymer.
On the other hand, Japanese Patent Application Laid-open No. Hei 7-53862 discloses a polyamide resin composition including: 100 parts by weight of a mixture of an aliphatic crystalline polyamide resin (60 to 90% by weight), a semiaromatic amorphous polyamide resin (0 to 20% by weight), and a phenol resin (5 to 30% by weight); and 50 to 200 parts by weight of a glass fiber.
Conventionally, a glass filler called E-glass or S-glass has been mainly used as reinforcing materials for polyamide resins in general.
However, the refractive index of the amorphous polyamide resins with respect to light having a wavelength of 589 nm (nD) is 1.50 to 1.54, while the refractive index of E-glass is about 1.555. Therefore, an amorphous polyamide resin molded product reinforced with E-glass has improved strength but has lowered transparency because of difference between the refractive indices. In addition, the refractive index of S-glass is about 1.521. In the case where there is no difference of the refractive indices between the S-glass and the amorphous polyamide resin, the transparency of an S-glass reinforced amorphous polyamide resin molded product is not impaired, but the melting temperature of S-glass is very high (about 1,800° C.), resulting in difficulty in producing a glass fiber.
In Japanese Patent Application Laid-open No. Hei 4-337355, the amorphous polyamide resin is reinforced with a glass fiber including E-glass, and hence a molded product of the amorphous polyamide resin has a total light transmittance of 56 to 71%, and has low transparency.
In Japanese Patent Application Laid-open No. Hei 7-53862, glass fiber is blended in an amorphous polyamide resin to improve the stiffness and mechanical strength, but is not considered about the transparency, and hence an attempt to adjust the refractive indices of the amorphous polyamide resin and the glass fiber by changing the composition of the glass fiber is not disclosed.